#5B6FC3

CSS

:root {
  --loch-ness: #5b6fc3;
  --loch-ness-rgb: 91 111 195;
  --loch-ness-oklch: oklch(0.566 0.132 271.5);
}

.element {
  color: var(--loch-ness);
  background-color: hsl(228 46% 56%);
  border-color: oklch(0.566 0.132 271.5);
}

Tailwind CSS v4

@theme {
  --color-loch-ness: #5b6fc3;
  --color-loch-ness-50: #e9f3ff;
  --color-loch-ness-100: #d9e6ff;
  --color-loch-ness-200: #c2d1ff;
  --color-loch-ness-300: #a2b3fb;
  --color-loch-ness-400: #8399ec;
  --color-loch-ness-500: #687edd;
  --color-loch-ness-600: #586bba;
  --color-loch-ness-700: #465696;
  --color-loch-ness-800: #303f70;
  --color-loch-ness-900: #212b4f;
  --color-loch-ness-950: #101834;
}

SCSS

$loch-ness: #5b6fc3;
$loch-ness-rgb: 91, 111, 195;
$loch-ness-light: mix(#fff, $loch-ness, 20%);
$loch-ness-dark: mix(#000, $loch-ness, 20%);

.element {
  color: $loch-ness;
  box-shadow: 0 0 0 2px rgba($loch-ness, 0.35);
}